Well periphery crack forward modeling method and device based on remote detection electromagnetic wave logging

Abstract

According to the well periphery crack forward modeling simulation method and device based on the far exploration electromagnetic wave logging, through the boundary condition equivalent crack, the number of grids can be remarkably reduced, the solving freedom degree can be reduced, the calculation efficiency can be improved, and high-efficiency simulation of complex multi-scale crack low-frequency electromagnetic response is achieved; the method has important application value in evaluation of natural fractures and fracturing fractures of shale oil and gas and compact oil and gas reservoirs.

Description

Technical Field

[0001] The invention relates to the technical field of geophysical logging characterization of wellside structures, and in particular to a forward simulation method and device for wellbore perimeter fractures based on remote detection electromagnetic wave logging. Background Art

[0002] The development of shale oil and tight oil and gas reservoirs is the key to increasing and stabilizing oil and gas production. The matrix porosity and permeability of this type of reservoir are low, and they must be transformed through natural fractures or hydraulic fracturing to generate fractures that are conducive to the flow of oil and gas before they have economic mining value. Therefore, the evaluation of natural fractures or hydraulic fractures plays an important role in guiding fracturing operations and improving recovery.

[0003] The long-range electromagnetic wave logging instrument is a low-frequency electromagnetic induction logging instrument in the well, which has good application prospects in the field of evaluating natural fractures and hydraulic fractures. In order to use the long-range electromagnetic wave logging instrument to achieve effective evaluation of fractures, it is necessary to establish a numerical simulation algorithm for the fracture response of long-range electromagnetic wave logging. The fracture morphology is irregular. When simulating the response of long-range electromagnetic wave logging in fractured formations, the ability of finite elements to process complex geometric bodies is more suitable. However, the scale difference between the opening and extension depth of the fracture is too large. When the fracture is discretized into a solid mesh, a large number of filling units will be generated, and the degree of freedom of the solution will increase sharply. It not only consumes a huge amount of computing resources, but also when the fracture extension is relatively long or there are multiple complex fractures, the meshing is prone to fail, resulting in the long-range electromagnetic wave logging response of these models cannot be solved. Summary of the invention

[0004] The present invention provides a forward modeling method and device for wellbore fractures based on remote detection electromagnetic wave logging, which are used to realize rapid and accurate simulation of electromagnetic response of wellbore fractures.

[0005] In a first aspect, the present invention provides a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging, comprising:

[0006] According to the acquired target well and peri-well fracture information, a corresponding formation model including the wellbore, peri-well fractures and peri-well formations is established;

[0007] Determine a target fracture in the formation model that meets the equivalent requirements of boundary conditions, and introduce the target fracture into the right-hand end term of the unit;

[0008] Using a grid generation technique, the part of the formation model except the target fracture is discretized into continuous tiny units to form a corresponding grid topological relationship;

[0009] Selecting the background medium resistivity value of the formation model, and obtaining the electromagnetic field background field distribution value by using an analytical algorithm;

[0010] According to the interpolation basis function, the unit left-end term and the unit right-end term are determined, and in combination with the grid topological relationship, the unit left-end term and the unit right-end term are assembled into a large sparse linear equation group, and the electromagnetic field scattered field distribution value is obtained by solving, and combined with the electromagnetic field background field distribution value, the total electromagnetic field is obtained;

[0011] Based on the total electromagnetic field, a remote detection electromagnetic wave logging response is obtained.

[0012] Optionally, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right-hand side term of the unit, comprises:

[0013] Selecting cracks with high conductivity, crack curvature radius greater than the corresponding crack thickness, and crack thickness less than 1 / 100 of the crack extension length from the wellbore cracks in sequence as the target cracks;

[0014] The target crack is equivalent to the target crack through boundary conditions, and the right-hand side term of the unit is introduced.

[0015] Optionally, according to the interpolation basis function, the unit left-end term and the unit right-end term are determined, and in combination with the grid topological relationship, the unit left-end term and the unit right-end term are assembled into a large sparse linear equation group, and the electromagnetic field scattered field distribution value is obtained by solving, and in combination with the electromagnetic field background field distribution value, the total electromagnetic field is obtained, including:

[0016] By constructing the interpolation basis function, the left-end term of the unit corresponding to the electromagnetic field scattering field is calculated;

[0017] Calculate the right-hand side term of the unit by using the right-hand side term formula;

[0018] Based on the grid topological relationship, the unit left-end terms and the unit right-end terms are assembled into a large sparse linear equation group, and the electromagnetic field scattering field distribution value is obtained by solving the equation group.

[0019] Optionally, the interpolation basis function is constructed to calculate the left-hand term of the unit corresponding to the electromagnetic field scattering field, including:

[0020] By constructing the interpolation basis function, the electromagnetic field scattering field is discretized;

[0021] The left-hand term of the unit corresponding to the discrete unit is calculated by using the stiffness matrix formula and the density matrix formula corresponding to the interpolation basis function.

[0022] Optionally, the right-hand side term of the unit is calculated by a right-hand side term formula, including:

[0023] Determining whether the unit contains the target crack;

[0024] If not, the right-hand side term of the unit is calculated using the interpolation basis function and the electromagnetic field background field;

[0025] If so, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand term of the unit, and the boundary conditions satisfied by the tangential component of the electric field intensity of the target fracture are added to equalize the fracture in the formation.

[0026] Optionally, obtaining a remote detection electromagnetic wave logging response based on the total electromagnetic field includes:

[0027] In the location unit including the receiving coil, interpolation processing is performed on the total electromagnetic field to obtain the magnetic field at the center of the receiving coil or the electric field on the coil conductor;

[0028] Based on the magnetic field at the center of the receiving coil or the electric field on the coil conductor, the remote detection electromagnetic wave logging response is obtained through Maxwell equations or integration along the conductor.

[0029] In a second aspect, the present invention provides a forward simulation device for wellbore fractures based on remote detection electromagnetic wave logging, comprising:

[0030] A model building module is used to build a corresponding formation model including the wellbore, the fractures around the well and the formations around the well according to the acquired target well and the fractures around the well;

[0031] A judgment module, used for determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right end term of the unit;

[0032] A grid topology relationship forming module is used to discretize the part of the formation model except the target fracture into continuous tiny units by using grid partitioning technology to form a corresponding grid topology relationship;

[0033] A background field analytical calculation module is used to select the background medium resistivity value of the formation model and obtain the electromagnetic field background field distribution value using an analytical algorithm;

[0034] An electromagnetic field scattered field distribution value determination module is used to determine the unit left-end term and the unit right-end term according to the interpolation basis function, combine the unit left-end term and the unit right-end term into a large sparse linear equation group in combination with the grid topological relationship, solve and obtain the electromagnetic field scattered field distribution value, and combine with the electromagnetic field background field distribution value to obtain the total electromagnetic field;

[0035] The response module is used to obtain the remote detection electromagnetic wave logging response based on the total electromagnetic field.

[0036] Optionally, the judging module includes:

[0037] A judgment submodule, for selecting, from the wellbore fractures, fractures with high conductivity, fracture curvature radius greater than the corresponding fracture thickness, and fracture thickness less than 1 / 100 of the fracture extension length as the target fractures;

[0038] The introduction submodule is used to equalize the target crack through boundary conditions and introduce the right-hand side term of the unit.

[0039] In a third aspect, the present application provides an electronic device, comprising a processor and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the steps in the method provided in the first aspect are performed.

[0040] In a fourth aspect, the present application provides a storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the steps in the method provided in the first aspect are performed.

[0041] It can be seen from the above technical solutions that the present invention has the following advantages:

[0042] The present invention provides a forward modeling method and device for wellbore fractures based on remote detection electromagnetic wave logging. The method comprises: establishing a corresponding formation model including a wellbore, wellbore fractures and wellbore formations according to acquired target well and wellbore fracture information; determining a target fracture in the formation model that meets the boundary condition equivalent requirement, and introducing the target fracture into a unit right-end term; using a grid partitioning technology, discretizing the part of the formation model except the target fracture into continuous tiny units to form a corresponding grid topological relationship; selecting the background medium resistivity value of the formation model, and obtaining an electromagnetic field background field distribution value by using an analytical algorithm; determining a unit left-end term and a unit right-end term according to an interpolation basis function, combining the grid topological relationship, assembling the unit left-end term and the unit right-end term into a large sparse linear equation group, solving to obtain an electromagnetic field scattering field distribution value, and combining the electromagnetic field background field distribution value to obtain an electromagnetic field total field; based on the electromagnetic field total field, obtaining a remote detection electromagnetic wave logging response. Replacing fractures with boundary conditions can significantly reduce the number of grids, reduce the degrees of freedom in solving, improve computational efficiency, and achieve efficient simulation of low-frequency electromagnetic responses of complex multi-scale fractures. It has important application value in the evaluation of natural fractures and hydraulic fractures in shale oil and gas and tight oil and gas reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1 This is a flow chart of a first embodiment of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention;

[0045] Figure 2 A schematic diagram of boundary conditions of equivalent fractures in Embodiment 1 of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging of the present invention;

[0046] Figure 3 This is a flow chart of the second embodiment of a forward simulation method for wellbore fractures based on remote detection electromagnetic wave logging of the present invention;

[0047] Figure 4 This is a flowchart of a third embodiment of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention;

[0048] Figure 5 This is a schematic diagram of the solid mesh division when the crack does not use equivalent boundary conditions;

[0049] Figure 6 Schematic diagram of mesh generation after applying equivalent boundary conditions to cracks;

[0050] Figure 7 This is a comparison chart of the equivalent amplitude ratio signals of a 1cm crack with and without boundary conditions;

[0051] Figure 8 This is a comparison diagram of the phase difference signal when the crack with 1cm opening is equivalent to the boundary condition and when the crack without boundary condition is equivalent to the boundary condition.

[0052] Fig. 9 This is the comparison chart of the equivalent amplitude ratio signal of the 3mm opening crack with and without boundary conditions;

[0053] Fig.10 This is a comparison chart of the phase difference signals when the crack with 3mm opening is equivalent to the boundary condition and when it is not equivalent to the boundary condition;

[0054] Fig.11 A comparison chart of relative errors of amplitude ratios after applying boundary conditions to equivalent fractures with different openings;

[0055] Fig.12 This is a comparison diagram of relative errors of phase difference after applying boundary conditions to cracks with different openings;

[0056] Fig.13 The present invention is a structural block diagram of an embodiment of a forward simulation device for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention. DETAILED DESCRIPTION

[0057] The embodiment of the present invention provides a forward modeling method and device for wellbore fractures based on remote detection electromagnetic wave logging, which are used to achieve rapid and accurate simulation of electromagnetic responses of wellbore fractures.

[0058] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] For example, see Figure 1 , Figure 1 The flowchart of the first embodiment of the forward modeling method of wellbore fractures based on remote detection electromagnetic wave logging of the present invention includes:

[0060] S101, establishing a corresponding formation model including the wellbore, the fractures around the well and the formations around the well according to the acquired target well and the fractures around the well;

[0061] In an embodiment of the present invention, the established formation model includes the wellbore and the formations near the well, which may also include one or more of natural fractures around the well, hydraulic fractures, and other geological structures near the well. The wellbore distribution and attribute information such as radius, resistivity, dielectric constant, etc. are set; the formation distribution and attribute information such as the position of the formation interface, the resistivity and dielectric constant of different layers, etc.; the number, distribution and attributes of the cracks around the well, and the characteristic scale of the cracks is extracted, including but not limited to the position, shape, opening and extension length of the cracks.

[0062] S102, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right end term of the unit;

[0063] In an optional embodiment, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions and introducing the target fracture into the right-hand side term of the unit includes:

[0064] Selecting cracks with high conductivity, crack curvature radius greater than the corresponding crack thickness, and crack thickness less than 1 / 100 of the crack extension length from the wellbore cracks in sequence as the target cracks;

[0065] The target crack is equivalent to the target crack through boundary conditions, and the right-hand side term of the unit is introduced.

[0066] In an embodiment of the present invention, a conventional electromagnetic field finite element calculation method is used. After the right-hand side term of the calculation unit is calculated using basis functions and background fields, if the unit contains a fracture that meets the boundary condition equivalence requirements, the boundary condition satisfied by the tangential component of the electric field intensity on the fracture boundary is added on the basis of the right end of the conventional unit to equivalent the fracture in the formation, and the target fracture is no longer subjected to solid mesh division, thereby reducing the number of meshes and improving the calculation speed while ensuring the calculation accuracy.

[0067] In the specific implementation, the conditions for judging whether a crack can be equivalent to a boundary condition include: (1) the crack has high conductivity, in which case it can be assumed that the waves inside the conductor propagate only perpendicular to the conductor surface; (2) the crack curvature radius should be greater than its thickness; (3) the crack thickness is much smaller than the crack extension length (less than 1 / 100 of the crack extension length). Please refer to Figure 2 , FIG. 1 is a schematic diagram of boundary conditions of equivalent fractures in Embodiment 1 of a forward simulation method for wellbore fractures based on remote detection electromagnetic wave logging of the present invention, and the specific boundary conditions are:

[0068]

[0069] in,

[0070]

[0071]

[0072]

[0073]

[0074] In the expression, E tan1 and E tan2 are the electric field components parallel to the interface in the media on both sides, Z 11 and Z 12 is the intermediate parameter, J s1 and J s2 are the surface current density in the media on both sides, H tan1 and H tan2 are the magnetic field components parallel to the interface in the media on both sides, and They represent the normal directions of the interfaces of the media on both sides, j is the imaginary unit, ω is the angular frequency, μ is the magnetic permeability of the medium, k is the wave number, and τ is the distance between the media on both sides.

[0075] S103, using a grid generation technology, discretizing the part of the formation model except the target fracture into continuous tiny units to form a corresponding grid topological relationship;

[0076] In the embodiment of the present invention, the formation model file and the fracture characteristic file of the formation model are read, and the formation model is discretized into small units using a grid partitioning technology, and the grid topological relationship is stored.

[0077] In the specific implementation, the fracture opening and the electrical contrast with the background medium in the formation model file and the fracture feature file are used to determine whether the fracture needs to be meshed. If the conditions are met, only the fracture boundary information is stored. If not, the frontier advancement method or other existing meshing techniques are used for meshing.

[0078] S104, selecting the background medium resistivity value of the formation model and obtaining the electromagnetic field background field distribution value by using an analytical algorithm;

[0079] It should be noted that the background medium is a virtual medium set for the convenience of numerical calculation, which represents the average distribution of the overall resistivity of the entire model. The background medium resistivity can be selected as the average resistivity of the entire model, or the resistivity when there are no cracks in the formation, or it can be determined by other existing background medium resistivity selection techniques such as the geometric factor method.

[0080] In the embodiment of the present invention, the resistivity of the formation without any cracks or other special geological bodies is directly used as the background medium resistivity, and the background field distribution value of the electromagnetic field is obtained by using an analytical algorithm.

[0081] S105, determining the unit left-end term and the unit right-end term according to the interpolation basis function, assembling the unit left-end term and the unit right-end term into a large sparse linear equation group in combination with the grid topological relationship, solving to obtain the electromagnetic field scattered field distribution value, and combining with the electromagnetic field background field distribution value to obtain the electromagnetic field total field;

[0082] It should be noted that the electromagnetic field scattering field distribution refers to the abnormal electromagnetic field distribution caused by the spatial resistivity difference when there is a difference in resistivity between the formation model and the virtual background medium. It indicates the disturbance of the electromagnetic field by cracks or other special geological bodies.

[0083] S106, obtaining a long-range detection electromagnetic wave logging response based on the total electromagnetic field.

[0084] It should be noted that the long-range detection electromagnetic wave instrument is generally composed of a transmitting short section and multiple receiving short sections, wherein the transmitting short section is equipped with one or more inclined transmitting coils, and the receiving short section is composed of one or more inclined coils, or three orthogonal receiving coils. According to the formation conditions, the source distance and frequency can be flexibly configured. Under normal circumstances, the operating frequency is usually set between 6kHz and 96kHz to ensure that the logging response has sufficient signal-to-noise ratio.

[0085] For example 2, please refer to Figure 3 , Figure 3 This is a flow chart of a second embodiment of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging of the present invention, the method comprising:

[0086] Step S201, establishing a corresponding formation model including the wellbore, the fractures around the well and the formations around the well according to the acquired target well and the fractures around the well;

[0087] Step S202, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right end term of the unit;

[0088] Step S203, using a grid generation technique, discretizing the part of the formation model except the target fracture into continuous tiny units to form a corresponding grid topological relationship;

[0089] Step S204, selecting the background medium resistivity value of the formation model and obtaining the electromagnetic field background field distribution value by using an analytical algorithm;

[0090] Step S205, calculating the left-end term of the unit corresponding to the electromagnetic field scattering field by constructing the interpolation basis function;

[0091] Step S206, calculating the right-hand side term of the unit by the right-hand side term formula;

[0092] Step S207, based on the grid topological relationship, assembling the unit left-end terms and the unit right-end terms into a large sparse linear equation group, and solving them to obtain the electromagnetic field scattering field distribution value;

[0093] In the embodiment of the present invention, based on the grid topology, the left-hand side and right-hand side of the unit are assembled into a large sparse linear equation system, and then the distribution of the electromagnetic field scattering field can be obtained by solving the equation system. The background field and the scattered field values ​​are added to obtain the total electromagnetic field.

[0094] Step S208: obtaining a remote detection electromagnetic wave logging response based on the total electromagnetic field.

[0095] For example 3, please refer to Figure 4 , Figure 4This is a flow chart of a third embodiment of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging of the present invention, the method comprising:

[0096] Step S301, establishing a corresponding formation model including the wellbore, the fractures around the well and the formations around the well according to the acquired target well and the fractures around the well;

[0097] Step S302, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right end term of the unit;

[0098] In an optional embodiment, determining a target fracture in the formation model that meets the boundary condition equivalent requirement and introducing the target fracture into the right-hand side term of the unit includes:

[0099] Selecting cracks with high conductivity, crack curvature radius greater than the corresponding crack thickness, and crack thickness less than 1 / 100 of the crack extension length from the wellbore cracks in sequence as the target cracks;

[0100] The target crack is equivalent to the target crack through boundary conditions, and the right-hand side term of the unit is introduced.

[0101] Step S303, using a grid generation technique, discretizing the part of the formation model except the target fracture into continuous tiny units to form a corresponding grid topological relationship;

[0102] Step S304, selecting the background medium resistivity value of the formation model and obtaining the electromagnetic field background field distribution value by using an analytical algorithm;

[0103] Step S305, discretizing the electromagnetic field scattering field by constructing the interpolation basis function;

[0104] Step S306, calculating the element left-end term corresponding to the discrete element by using the stiffness matrix formula and the density matrix formula corresponding to the interpolation basis function;

[0105] In the embodiment of the present invention, an interpolation basis function is constructed to perform numerical discretization on a tiny unit, and a stiffness matrix and a density matrix are calculated by a finite element equation to obtain the left-hand term of the unit.

[0106] Step S307, calculating the right-hand side term of the unit by the right-hand side term formula;

[0107] In an optional embodiment, the right-hand side term of the unit is calculated by the right-hand side term formula, including:

[0108] Determining whether the unit contains the target crack;

[0109] If not, the right-hand side term of the unit is calculated using the interpolation basis function and the electromagnetic field background field;

[0110] If so, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand term of the unit, and the boundary conditions satisfied by the tangential component of the electric field intensity of the target fracture are added to equalize the fracture in the formation.

[0111] Step S308, based on the grid topological relationship, assembling the unit left-end terms and the unit right-end terms into a large sparse linear equation group, and solving them to obtain the electromagnetic field scattering field distribution value;

[0112] Step S309, interpolating the total electromagnetic field in the location unit containing the receiving coil to obtain the magnetic field at the center of the receiving coil or the electric field on the coil conductor;

[0113] Step S310, based on the magnetic field at the center of the receiving coil or the electric field on the coil conductor, obtain the remote detection electromagnetic wave logging response through Maxwell equations or integration along the conductor.

[0114] In the embodiment of the present invention, the total electromagnetic field is interpolated in the location unit containing the receiving coil to obtain the magnetic field at the center of the receiving coil or the electric field on the coil wire. Further processing can synthesize and output the phase difference, amplitude ratio and other remote detection electromagnetic wave logging responses.

[0115] A forward simulation method for wellbore fractures based on remote detection electromagnetic wave logging provided in embodiments 1, 2 and 3 of the present invention comprises: establishing a corresponding formation model including a wellbore, wellbore fractures and wellbore formations according to the acquired target well and wellbore fracture information; determining a target fracture in the formation model that meets the boundary condition equivalent requirements, and introducing the target fracture into the right-hand end term of the unit; using a grid partitioning technique, discretizing the part of the formation model except the target fracture into continuous tiny units to form a corresponding grid topological relationship; selecting the background medium resistivity value of the formation model, and obtaining the electromagnetic field background field distribution value by an analytical algorithm; determining the unit left-hand end term and the unit right-hand end term according to an interpolation basis function, and assembling the unit left-hand end term and the unit right-hand end term into a large sparse linear equation group in combination with the grid topological relationship, solving the electromagnetic field scattering field distribution value, and obtaining the electromagnetic field total field in combination with the electromagnetic field background field distribution value; obtaining a remote detection electromagnetic wave logging response based on the total electromagnetic field. Replacing fractures with boundary conditions can significantly reduce the number of grids, reduce the degrees of freedom in solving, improve computational efficiency, and achieve efficient simulation of low-frequency electromagnetic responses of complex multi-scale fractures. It has important application value in the evaluation of natural fractures and hydraulic fractures in shale oil and gas and tight oil and gas reservoirs.

[0116] Example 4: Assume that there is a horizontal disk-shaped crack that cuts through the wellbore in the homogeneous medium. If the boundary condition equivalent crack is not used, the crack is divided by a solid grid. The grid after division is as follows: Figure 5 The solid mesh partitioning diagram when the boundary conditions are not used to equalize the fractures in the formation is shown in the schematic diagram. The fracture formation model is partitioned by using the boundary conditions to equalize the fractures in the formation. The mesh after partitioning is as follows Figure 6 The schematic diagram of the mesh division after the equivalent boundary conditions are applied to the crack is shown in the figure.

[0117] In the figure, the high conductivity fracture with a certain thickness is equivalent to the boundary condition, and the fracture entity is not segmented, which greatly reduces the number of grids and improves the calculation efficiency. When the fracture opening is 1cm and 3mm, the amplitude ratio and phase difference of the electromagnetic wave logging of the long-range detection of the uniform formation without fractures are shown in Figure 1. Figure 7 to Figure 10 As shown, Figure 7 This is a comparison chart of the equivalent amplitude ratio signals of a 1cm crack with and without boundary conditions. Figure 8 This is a comparison chart of the phase difference signal when the crack with 1cm opening is equivalent to the boundary condition and when it is not equivalent to the boundary condition. Fig. 9 This is a comparison chart of the equivalent amplitude ratio of a 3mm crack with and without boundary conditions. Fig.10 The comparison diagram of the phase difference signal with and without boundary conditions for a 3mm opening fracture shows that, at the same opening, the amplitude ratio and phase difference show obvious anomalies at the fracture, and the amplitude ratio and phase difference logging responses have good consistency.

[0118] Calculate the relative errors of the amplitude ratio and phase difference of the remote detection electromagnetic wave logging after applying the boundary conditions equivalent to different fracture openings, such as Fig.11 Comparison of relative errors of amplitude ratios of cracks with different openings after applying boundary conditions Fig.12 As shown in the phase difference relative error comparison diagram after applying boundary conditions to equivalent cracks with different openings, it can be seen that the relative error of the two methods for 3mm cracks is less than 1%, the relative error of 1cm cracks is less than 4%, and the relative error of 2cm cracks is less than 10%. The opening of natural cracks and hydraulic fractures in actual formations is generally less than 1cm, so the embodiment of the present invention can achieve high-precision simulation of cracks while significantly reducing the amount of calculation.

[0119] For example 5, please refer to Fig.13 , Fig.13 The present invention is a structural block diagram of an embodiment of a forward simulation device for wellbore fractures based on remote detection electromagnetic wave logging, comprising:

[0120] The model building module 501 is used to build a corresponding formation model including the wellbore, the fractures around the well and the formations around the well according to the acquired target well and the fractures around the well;

[0121] A judgment module 502 is used to determine a target fracture in the formation model that meets the boundary condition equivalent requirement, and introduce the target fracture into the right end term of the unit;

[0122] A grid topology relationship forming module 503 is used to discretize the part of the formation model except the target fracture into continuous tiny units by using a grid partitioning technology to form a corresponding grid topology relationship;

[0123] Background field analytical calculation module 504, used to select the background medium resistivity value of the formation model and obtain the electromagnetic field background field distribution value by using analytical algorithm;

[0124] The electromagnetic field scattered field distribution value determination module 505 is used to determine the unit left end term and the unit right end term according to the interpolation basis function, combine the unit left end term and the unit right end term into a large sparse linear equation group in combination with the grid topological relationship, solve and obtain the electromagnetic field scattered field distribution value, and combine with the electromagnetic field background field distribution value to obtain the total electromagnetic field;

[0125] The response module 506 is used to obtain a remote detection electromagnetic wave logging response based on the total electromagnetic field.

[0126] In an optional embodiment, the determining module 502 includes:

[0127] A judgment submodule, for selecting, from the wellbore fractures, fractures with high conductivity, fracture curvature radius greater than the corresponding fracture thickness, and fracture thickness less than 1 / 100 of the fracture extension length as the target fractures;

[0128] The introduction submodule is used to equalize the target crack through boundary conditions and introduce the right-hand side term of the unit.

[0129] In an optional embodiment, the electromagnetic field scattering field distribution value determination module 505 includes:

[0130] A unit left-end term determination submodule, used to calculate the unit left-end term corresponding to the electromagnetic field scattering field by constructing the interpolation basis function;

[0131] A unit right-hand term determination submodule, used to calculate the unit right-hand term through a right-hand term formula;

[0132] The electromagnetic field scattering field distribution value determination submodule is used to assemble the unit left-end terms and the unit right-end terms into a large sparse linear equation group based on the grid topological relationship, and solve them to obtain the electromagnetic field scattering field distribution value.

[0133] In an optional embodiment, the unit left end item determination submodule includes:

[0134] A discrete submodule, used for discretizing the electromagnetic field scattering field by constructing the interpolation basis function;

[0135] The unit left-end term determines the unit, which is used to calculate the unit left-end term corresponding to the discrete unit through the stiffness matrix formula and the density matrix formula corresponding to the interpolation basis function.

[0136] In an optional embodiment, the unit right end item determination submodule includes:

[0137] A judgment unit is used to judge whether the unit contains the target fracture; if not, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand side term of the unit; if so, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand side term of the unit, and the boundary conditions satisfied by the tangential component of the electric field intensity of the target fracture are added to obtain the fracture in the equivalent formation.

[0138] In an optional embodiment, the response module 506 includes:

[0139] An interpolation submodule, used to perform interpolation processing on the total electromagnetic field in a position unit including a receiving coil to obtain a magnetic field at the center of the receiving coil or an electric field on the coil conductor;

[0140] The response submodule is used to obtain the remote detection electromagnetic wave logging response based on the magnetic field at the center of the receiving coil or the electric field on the coil wire through Maxwell equations or integration along the wire.

[0141] An embodiment of the present invention also provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of a forward simulation method for wellbore fractures based on remote detection electromagnetic wave logging as described in any of the above embodiments.

[0142] An embodiment of the present invention further provides a computer storage medium having a computer program stored thereon. When the computer program is executed by the processor, the steps of a forward simulation method for wellbore fractures based on remote detection electromagnetic wave logging as described in any of the above embodiments are implemented.

[0143] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0144] In the several embodiments provided in the present application, it should be understood that the methods, devices, electronic devices and storage media disclosed in the present invention can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0145] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0146] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0147] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a readable storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned readable storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0148] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging, characterized in that: include: According to the acquired target well and peri-well fracture information, a corresponding formation model including the wellbore, peri-well fractures and peri-well formations is established; Determine a target fracture in the formation model that meets the equivalent requirements of boundary conditions, and introduce the target fracture into the right-hand end term of the unit; Using a grid generation technique, the part of the formation model except the target fracture is discretized into continuous tiny units to form a corresponding grid topological relationship; Selecting the background medium resistivity value of the formation model, and obtaining the electromagnetic field background field distribution value by using an analytical algorithm; According to the interpolation basis function, the unit left-end term and the unit right-end term are determined, and in combination with the grid topological relationship, the unit left-end term and the unit right-end term are assembled into a large sparse linear equation group, and the electromagnetic field scattered field distribution value is obtained by solving, and combined with the electromagnetic field background field distribution value, the total electromagnetic field is obtained; Based on the total electromagnetic field, a remote detection electromagnetic wave logging response is obtained.

2. The forward simulation method of wellbore fractures based on remote detection electromagnetic wave logging according to claim 1, characterized in that: Determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right-hand side term of the unit, including: Selecting cracks with high conductivity, crack curvature radius greater than the corresponding crack thickness, and crack thickness less than 1 / 100 of the crack extension length from the wellbore cracks in sequence as the target cracks; The target crack is equivalent to the target crack through boundary conditions, and the right-hand side term of the unit is introduced.

3. The forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to claim 1, characterized in that: According to the interpolation basis function, the unit left-end term and the unit right-end term are determined, and combined with the grid topological relationship, the unit left-end term and the unit right-end term are assembled into a large sparse linear equation group, and the electromagnetic field scattered field distribution value is obtained by solving, and combined with the electromagnetic field background field distribution value, the electromagnetic field total field is obtained, including: By constructing the interpolation basis function, the left-end term of the unit corresponding to the electromagnetic field scattering field is calculated; Calculate the right-hand side term of the unit by using the right-hand side term formula; Based on the grid topological relationship, the unit left-end terms and the unit right-end terms are assembled into a large sparse linear equation group, and the electromagnetic field scattering field distribution value is obtained by solving the equation group.

4. The forward simulation method of wellbore fractures based on remote detection electromagnetic wave logging according to claim 3 is characterized in that: By constructing the interpolation basis function, the left-hand term of the unit corresponding to the electromagnetic field scattering field is calculated, including: By constructing the interpolation basis function, the electromagnetic field scattering field is discretized; The left-hand term of the unit corresponding to the discrete unit is calculated by using the stiffness matrix formula and the density matrix formula corresponding to the interpolation basis function.

5. The forward simulation method of wellbore fractures based on remote detection electromagnetic wave logging according to claim 3, characterized in that: The right-hand side of the cell is calculated using the right-hand side formula, including: Determining whether the unit contains the target crack; If not, the right-hand side term of the unit is calculated using the interpolation basis function and the electromagnetic field background field; If so, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand term of the unit, and the boundary conditions satisfied by the tangential component of the electric field intensity of the target fracture are added to equalize the fracture in the formation.

6. The forward simulation method of wellbore fractures based on remote detection electromagnetic wave logging according to claim 1, characterized in that: Based on the total electromagnetic field, a remote detection electromagnetic wave logging response is obtained, including: In the location unit including the receiving coil, interpolation processing is performed on the total electromagnetic field to obtain the magnetic field at the center of the receiving coil or the electric field on the coil conductor; Based on the magnetic field at the center of the receiving coil or the electric field on the coil conductor, the remote detection electromagnetic wave logging response is obtained through Maxwell equations or integration along the conductor.

7. A forward simulation device for wellbore fractures based on remote detection electromagnetic wave logging, characterized in that: include: A model building module is used to build a corresponding formation model including the wellbore, the fractures around the well and the formations around the well according to the acquired target well and the fractures around the well; A judgment module, used for determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right end term of the unit; A grid topology relationship forming module is used to discretize the part of the formation model except the target fracture into continuous tiny units by using grid partitioning technology to form a corresponding grid topology relationship; A background field analytical calculation module is used to select the background medium resistivity value of the formation model and obtain the electromagnetic field background field distribution value using an analytical algorithm; An electromagnetic field scattered field distribution value determination module is used to determine the unit left-end term and the unit right-end term according to the interpolation basis function, combine the unit left-end term and the unit right-end term into a large sparse linear equation group in combination with the grid topological relationship, solve and obtain the electromagnetic field scattered field distribution value, and combine with the electromagnetic field background field distribution value to obtain the total electromagnetic field; The response module is used to obtain the remote detection electromagnetic wave logging response based on the total electromagnetic field.

8. The forward simulation device for wellbore fractures based on remote detection electromagnetic wave logging according to claim 7, characterized in that: The judging module comprises: A judgment submodule, for selecting, from the wellbore fractures, fractures with high conductivity, fracture curvature radius greater than the corresponding fracture thickness, and fracture thickness less than 1 / 100 of the fracture extension length as the target fractures; The introduction submodule is used to equalize the target crack through boundary conditions and introduce the right-hand side term of the unit.

9. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the method according to any one of claims 1 to 6 is executed.

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 6 is performed.

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